Gene Regulation and the Order of the Operon (2023)


Explore gene expression with the Amoeba Sisters, including the fascinating Lac Operon found in bacteria! Learn how genes can be turned "on" and "off" and why this is essential for cellular function. Check out our FREE video handouts on!

⭐We have a menu of our resources that complement our videos! Visit

The Amoeba Sisters videos demystify science with humor and relevance. The videos center on Pinky's certification and experience in teaching biology at the high school level. For more information about The Amoeba Sisters, visit:

We cover the basics in biology concepts at the secondary level. If you are looking to discover more about biology and go into depth beyond these basics, our recommended reference is the FREE, peer reviewed, open source OpenStax biology textbook:

*Further Reading*
As our pinned comment mentions, we cover basics with the goal of inspiring curiosity for more! There are so many important details to explore. For example, the conversion of lactose to allolactose, the cAMP-CAP conversion that stimulates the RNA polymerase, or the names of the different genes and their individual functions. We also don't mention that there are other factors that can affect the activation of this operon (such as glucose levels). Check out this further reading suggestion in OpenStax Microbiology to learn more:


Support Us?

Our Resources:
Biology Playlist:
Unlectured Series:

Connect with us!

Visit our Redbubble store at

Want to learn tips for viewing edu YouTube videos including changing the speed, language, viewing the transcript, etc?

Music in this video is listed free to use/no attribution required from the YouTube audio library

We take pride in our AWESOME community, and we welcome feedback and discussion. However, please remember that this is an education channel. See YouTube's community guidelines and how YouTube handles comments that are reported by the community. We also reserve the right to remove comments.


Thank you so much to:
Anna Maria Rossolini for Italian subtitles!
Alisha Aggarwal for Hindi subtitles!

While we don't allow dubbing of our videos, we do gladly accept subtitle translations from our community. Some translated subtitles on our videos were translated by the community using YouTube's community-contributed subtitle feature. After the feature was discontinued by YouTube, we have another option for submitting translated subtitles here: We want to thank our amazing community for the generosity of their time in continuing to create translated subtitles. If you have a concern about community contributed contributions, please contact us.


Captioning is on! Click the CC button at bottom right to turn off.

Follow, the amoebas on Twitter, (@amoebasisters) and Facebook! Have.

You ever thought about how disastrous it could be if the cells in your eyes started producing the same hydrochloric acid that is made by your stomach cells? Your stomach cells produce HCL to help break down food, but you definitely don’t want that in your eyes.

Thank, goodness that doesn’t happen! But it’s surprising---because, both your eye cells and stomach cells contain all of your DNA.

All of your DNA is found in your body cells, but see---the portions that are used need to be regulated.



We could end up with something ridiculous.

Like…Eye cells producing digestive enzymes.

And that wouldn’t just be a waste of resources---that, would actually be very difficult to explain to your friends.You want some genes to be regulated.


Remember that genes are made up of DNA.

Dna is used to give instructions for the production of proteins in the process of protein synthesis.


An important concept is that there needs to be a method of determining which genes will be turned on and which genes will be turned.


This is called gene regulation.

There are many ways that genes are regulated., In, your human body cells.

You can have proteins that can bind to certain gene regions to increase the rate of transcription for the transcription enzyme, RNA polymerase.


You can have proteins decrease transcription to the point that it may not be transcribed at all.

That is a form of gene regulation., Your eye cells.

Don’t use the portion of DNA that codes for making HCL like your stomach cells do, because there is regulation like this in all of your cells to determine which portions of DNA is used.


We want to shift gears now to talk about a very interesting way of regulating genes that can sometimes be challenging to visualize.

A way that has not been found in humans, but instead is found in prokaryotes----with a few eukaryote exceptions.

It’s called an operon.

An operon is a fancy way of regulating genes and it usually is made up of a few genes that involve enzymes.

Remember, that enzymes are proteins with the ability to break down or build up the substances that they act.


Let’s talk about some key players in an operon, so we can see some gene regulation., First, RNA, polymerase., It’s, a builder- a builder enzyme, actually because RNA polymerase is an enzyme.

Remember that many things in biology that end in that –ase are enzymes.

Rna polymerase is needed in order to start transcription.


That transcription and translation are steps in protein synthesis.

Protein synthesis, which means to make proteins---enzymes in this case.

The thing about RNA polymerase though---it gets a little confusing for RNA polymerase.

Without somewhere to bind.


You watched our DNA replication video, you learned about DNA polymerase and how it needs to have a primer to know where to start.

Well, RNA Polymerase needs a promoter.

A promoter is a sequence of DNA.

Where RNA polymerase can bind to.


You would think that’s it---you get RNA polymerase attached to a promoter and boom! You make your mRNA, which eventually will be used to make a protein right? But there’s, this other sequence of DNA called an operator.

The operator, is a part of the DNA where something called a repressor can bind.

The big bad repressor, if bound to the operator, blocks.

Rna polymerase., Poor, RNA polymerase cannot move forward and no mRNA can be made.

Therefore, no proteins.

So take a look at our setup.


This is an example called a Lac Operon.


There is a promoter region of the DNA, the operator region of the DNA, and these are three genes: {have labeled, lacZ, lacY, and lacA).

That code for enzymes that help in the process of breaking down lactose.

Lactose is a sugar.

If lactose sugar is around.

Bacteria want these enzymes to be made, so they can use them to break down the lactose sugar.

Then they can metabolize it! Fed bacteria are happy.


Here’s, the repressor.


Actually, a gene here on the operon that codes for producing the repressor.


This gene that we call “I”? It has its own promoter.

This codes for the production of the repressor.


Why do we need this repressor? Well, it’s wasteful to make things that you don’t need., If there’s, no lactose,? It wouldn’t make sense to start making enzymes that work together to break down lactose.

It would be a waste---the.

Enzymes would just sit there.


If lactose is not present, then the repressor binds to the operator.

This blocks.

Rna polymerase.

mRNA cannot be made.


Therefore, the proteins---enzymes in this case---cannot be made.


If lactose is around in the environment, something pretty cool, happens.

The lactose---remember, that’s the sugar, binds to the repressor.

This changes the repressor’s conformation.

Try, as it might----the repressor can’t bind to the operator.

RNA polymerase finds its promoter, binds, and transcribes to make mRNA from the genes on the operon.

That mRNA will be used to make enzymes to break down that lactose sugar.

Bacteria like to eat so…that makes them pretty happy.

We have to say that we think it is pretty impressive to think about all the gene regulation that goes on in cells---and.

If you find it fascinating---know that there are careers that focus on gene regulation., By understanding how genes can be turned on and off, we can also gain a better understanding of treating a variety of diseases that have gene influences in the human body.

Well, that’s it for the amoeba sisters, and we remind you to stay curious!.


Gene Regulation and the Order of the Operon? ›

Structural, operator, regulator, promoter.

What is the correct order of genes in an operon? ›

Structural, operator, regulator, promoter.

What do you already know about gene regulation and the order of the operon? ›

Each operon contains regulatory DNA sequences, which act as binding sites for regulatory proteins that promote or inhibit transcription. Regulatory proteins often bind to small molecules, which can make the protein active or inactive by changing its ability to bind DNA.

In what order do the levels of gene regulation take place? ›

Regulation of gene expression can happen at any of the stages as DNA is transcribed into mRNA and mRNA is translated into protein. For convenience, regulation is divided into five levels: epigenetic, transcriptional, post-transcriptional, translational, and post-translational (Figure 17.6).

How is gene regulated via operon system? ›

operon, genetic regulatory system found in bacteria and their viruses in which genes coding for functionally related proteins are clustered along the DNA. This feature allows protein synthesis to be controlled coordinately in response to the needs of the cell.

What are the stages of lac operon? ›

This sequence illustrates different stages of the lac operon including the action of RNA polymerase (a), transcription (b), translation (c), repressor inhibition (d), and lactose-repressor interaction (e, f). ...

What is the first control sequence in an operon? ›

The operon discussed here is the lac operon, for "lactose." The first control sequence, the promoter, is the site where RNA polymerase attaches to the DNA. (Recall that RNA polymerase transcribes genes by making mRNA.) Between the promoter and the enzyme genes is a second control sequence called the operator.

What is the process of gene regulation? ›

The process of turning genes on and off is known as gene regulation. Gene regulation is an important part of normal development. Genes are turned on and off in different patterns during development to make a brain cell look and act different from a liver cell or a muscle cell, for example.

What are five different stages or levels at which gene expression is regulated? ›

Control of gene expression in eukaryotic cells occurs at epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels. Post-translational control refers to the: regulation of gene expression after transcription.

What are the three levels of gene regulation? ›

transcriptional control (whether and how much a gene is transcribed into mRNA) translational control (whether and how much an mRNA is translated into protein) post-translational control (whether the protein is in an active or inactive form, and whether the protein is stable or degraded)

What is the first step of gene regulation? ›

The process of gene transcription begins when an enzyme called polymerase II (Pol II) and other factors assemble at a DNA sequence upstream from a gene at a spot called a promoter.

What is the most important step in gene regulation? ›

Initiation of transcription is the most important step in gene expression. Without the initiation of transcription, and the subsequent transcription of the gene into mRNA by RNA polymerase, the phenotype controlled by the gene will not be seen.

What are the 4 levels of gene regulation in eukaryotes? ›

Control of gene expression in eukaryotic cells occurs at epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels.

What are the parts of the operon? ›

There are three components of an operon namely- the operator gene, promoter gene, and regulatory gene.

What are the main steps of gene regulation in eukaryotic cells in the correct order? ›

Stages of eukaryotic gene expression (any of which can be potentially regulated).
  • Chromatin structure. Chromatin may be tightly compacted or loose and open.
  • Transcription. ...
  • Processing and export. ...
  • mRNA stability. ...
  • Translation. ...
  • Protein processing.

What are the 4 major components of an operon mechanism? ›

Components of operon are regulator, promoter, operator and structural genes.

What are the 4 genes in the lac operon? ›

The lac operon consists of 3 structural genes, and a promoter, a terminator, regulator, and an operator. The three structural genes are: lacZ, lacY, and lacA. lacZ encodes β-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose.

What is the sequence of the lac operon in E. coli? ›

The lac operon in E. coli contains three structural genes, in addition to regulatory genes. The structural genes include: lacZ – which encodes the enzyme, β-galactosidase; lacY – which encodes the enzyme, lactose permease; and lacA – which encodes the enzyme, lactose transacetylase.

What is the regulation and control of the lac operon? ›

Regulation of the lac Operon

The activity of the promoter that controls the expression of the lac operon is regulated by two different proteins. One of the proteins prevents the RNA polymerase from transcribing (negative control), the other enhances the binding of RNA polymerase to the promoter (positive control).

How is an operon organized? ›

Bacterial mRNAs are organized into operons consisting of discrete open reading frames (ORFs) in a single polycistronic mRNA. Individual ORFs on the mRNA are differentially translated, with rates varying as much as 100-fold. The signals controlling differential translation are poorly understood.

What are the 3 types of genes in lac operon? ›

The lac operon consists of three structural genes: lacZ, which codes for β-galactosidase, which acts to cleave lactose into galactose and glucose; lacY, which codes for lac permease, which is a transmembrane protein necessary for lactose uptake; and lacA, which codes for a transacetylase that transfers an acetyl group ...

What are the parts of an operon and their function? ›

Operon Structure

They are made up of a promoter region, an operator, and multiple related genes. The operator can be located either within the promoter or between the promoter and the genes. RNA polymerase initiates transcription by binding to the promoter region.

What are the 3 enzymes produced by lac operon? ›

Three of the enzymes for lactose metabolism are grouped in the lac operon: lacZ, lacY, and lacA (Figure 12.1. 1).

What are the 4 ways of gene expression? ›

What is the process of gene expression? The process of gene expression is reading genes to create protein products for the cell. The process includes transcription, post-transcriptional modification, translation and protein folding.

At which of the following stages the gene expression is most commonly regulated? ›

Given this statistic, it is not surprising that the primary control point for gene expression is usually at the very beginning of the protein production process — the initiation of transcription. RNA transcription makes an efficient control point because many proteins can be made from a single mRNA molecule.

What are the stages of gene expression? ›

It consists of two major steps: transcription and translation. Together, transcription and translation are known as gene expression.

What do the 3 genes in the lac operon code for? ›

The lac operon consists of three structural genes: lacZ, which codes for β-galactosidase, which acts to cleave lactose into galactose and glucose; lacY, which codes for lac permease, which is a transmembrane protein necessary for lactose uptake; and lacA, which codes for a transacetylase that transfers an acetyl group ...

How many types of operons are there? ›

Operons are of two types: Inducible operon - This type of operon is activated where there is an inducer, e.g., Lac operon. Depression operon - It is usually seen in anabolic pathways. The operon is active whereas the functional product or enzyme is normally present in the cell.

What are 3 factors that can affect gene regulation? ›

The internal factors that can affect gene expression are:- hormones, metabolic products, and gender. The external factors that affect gene expression are chemicals, temperature, and light.

What are the levels of regulation? ›

There are three primary levels of regulation: registration, statutory certification, and licensure.

What is operon structure of genes? ›

An operon is a cluster of genes that are transcribed together to give a single messenger RNA (mRNA) molecule, which therefore encodes multiple proteins (Fig. 16.11). Such polycistronic mRNA is typically found in prokaryotes.

Does each gene in an operon have a start codon? ›

Operons encoding genes to be translated contain one or more start codons and ribosome binding sites (often known as Shine–Dalgarno sequences).

What are the 5 components of an operon? ›

This operon contains five structural genes: trp E, trp D, trp C, trp B, and trp A, which encodes tryptophan synthetase.

How many genes are regulated by lac operon? ›

The lac operon contains three genes: lacZ, lacY, and lacA. These genes are transcribed as a single mRNA, under control of one promoter.

What are the coding genes in lac operon? ›

The duo noted that the lac operon contains three genes that encode proteins involved in lactose metabolism. These are referred to as lac z, lac y, and lac a. The lac z gene encodes beta-galactosidase, the lac y gene encodes a permease, and the lac a gene encodes the transacetylase enzyme.

What are the types of operon? ›

Operons can be of two types:
  • Inducible – This type of operon is switched on in the presence of an inducer, e.g. Lac operon.
  • Repressible – It is usually present in anabolic pathways. The operon is active and the functional product or enzyme is present normally in the cell.

What is the relationship between a gene and operon? ›

Operons are a central feature of bacterial gene regulation (1). Each operon consists of a group of adjacent genes that are cotranscribed as a single mRNA. It is estimated that 50% of the genes in Escherichia coli are transcribed at least some of the time as part of an operon (2).

What is the sequence of ATG in DNA? ›

ATG (adenine-thymine-guanine) or AUG (adenine-uracil-guanine) is a codon, a sequence of three nucleotides in DNA or RNA that codes for a specific amino acid during protein synthesis.

What are genes in an operon quizlet? ›

Genes within an operon: Tend to be regulated by a common regulatory mechanism. Are generally involved in the same biochemical pathway. Are expressed as a polycistronic RNA.

Top Articles
Latest Posts
Article information

Author: Van Hayes

Last Updated: 01/11/2023

Views: 5237

Rating: 4.6 / 5 (46 voted)

Reviews: 85% of readers found this page helpful

Author information

Name: Van Hayes

Birthday: 1994-06-07

Address: 2004 Kling Rapid, New Destiny, MT 64658-2367

Phone: +512425013758

Job: National Farming Director

Hobby: Reading, Polo, Genealogy, amateur radio, Scouting, Stand-up comedy, Cryptography

Introduction: My name is Van Hayes, I am a thankful, friendly, smiling, calm, powerful, fine, enthusiastic person who loves writing and wants to share my knowledge and understanding with you.